FIELD OF THE INVENTION
The invention relates to a fuel assembly of a pressurized water nuclear reactor, including an upper and a lower cover plate to which guide tubes for control elements are fastened, spacers carried by the guide tubes, and a bundle of fuel rods disposed around the guide tubes and held in meshes of the spacers. The invention also relates to a method for producing a guide tube from zirconium alloys (zircaloy-2 or zircaloy-4) for a fuel assembly of a pressurized water reactor.
Guide tubes in pressurized water nuclear reactors, which are composed of zirconium alloys (zircaloy-2 and zircaloy-4), show sharp radiation-induced growth in the axial direction at the commencement of their use in a reactor core. If a fuel assembly is long enough to ensure that it is reliably held by guide pins of a core grid, the head of the fuel assembly may butt against the core grid as a result of the growth in length of the guide tubes. That may lead to warping of the guide tubes, causing the fuel assembly to be exchanged in order to avoid faults and damage.